The position of the gate mouth for injecting of thermoplastic material is commonly set to the terminal end of the extruding part forming a projecting bottom end of a key to make the flow of the material inside a mold on injection uniform. This also makes the mold structure simple in order to improve molding yield of a push-button switch integrated with a film, on which an display portion curved along the upper surface of the key top body made of thereon plastic material is printed. For this purpose the terminal end of the extruding part should be flat or a concave shape. A key switch has such contact portion such as a metal belleville spring with clicking touch and a resin film dome curved to the top direction on the bottom surface of a push-button switch integrated with a film, on which an display portion curved along the upper surface of the key top body made of thermoplastic material is printed thereon molded thermoplastic material. When the push-button switch is pushed, the terminal end of the extruding part projected in the bottom direction presses the metal belleville spring and the resin film dome to input a letter or symbol. By this reason, as shown in FIG. 7, the contact portion is frequently pushed without accurate contact between the center a of the extruding part 11 of the push-button and top b of the curved contact portion 12 with clicking touch. In this case, the clicking touch of the contact portion decreases and the contact portion cracks by residual stress.